Prion disease is characterized by neurodegeneration, prion protein (PrP) conformational change, and prion infectivity. Although the physical nature of infectious agent is still debated, compelling evidence favors the prion hypothesis, which postulates that the conversion from -helical-rich PrPC to -sheet-rich and protease-resistant PrPSc conformation is central to prion infectivity. Recent studies suggest a key role of other physiological factor(s) in facilitating PrP conversion and generation of prion infectivity. As a GPI-anchored protein, PrP is constantly exposed to the environment of membrane lipids and a PrP-lipid interaction has been demonstrated. The PrP binding to anionic lipids results in PrP conformational change and an alteration in lipid membrane permeability. Under an environment reminiscent of physiological conditions, the anionic lipid-PrP interaction converts a significant portion of full-length recombinant PrP into a conformation with increased -sheet content and a PrPSc-like proteinase K resistant pattern. Moreover, the biological relevance of PrP-lipid interaction is indicated by the influence of disease-associated mutation and the many characteristics shared by lipid-induced PrP conversion and PrPSc propagation. We propose the following studies to elucidate the contributions from lipid membrane to the pathogenesis of prion disease. In Aim 1, the pathophysiological significance of PrP-lipid interaction will be determined using our established in vitro assays to dissect the interaction between PrP and lipid. In addition, the influence of disease-associated PrP mutations on PrP-lipid interaction will be analyzed. In Aim 2, biochemical and animal studies will be used to determine the relationship among lipids, lipid induced PrP conformation and the self-perpetuating characteristic of prion. In Aim 3, the importance of non-raft localized PrP to prion infection-caused pathogenic changes will be studied using a novel transgenic mouse approach. We anticipate that our proposed studies will provide us with insights into the pathogenesis of prion disease and form the basis for developing rational therapeutic and prophylactic strategies. Results from these studies may also be relevant to other neurodegenerative disorders such as Alzheimer and Parkinson's diseases, in which protein-lipid membrane interactions have been proposed as a common pathogenic process. Prion diseases are a group of infectious neurodegenerative diseases. Our goal of this proposal is to understand how the pathogenic changes occur in prion disease. This knowledge will form the basis for developing rationale preventive and therapeutic approaches against these devastating and incurable dieseases.